Decreasing costs, state and federal tax incentives, and increased awareness of the correlation between greenhouse gasses (e.g., carbon dioxide emissions) and climate change have increased the popularity of photovoltaic (PV) or “solar” energy generation systems with consumers, businesses and utility companies. A conventional solar energy generation system includes an array of PV modules connected together on one or more strings, a combiner for combining direct current (DC) outputs of the one or more strings, one or more string inverters for converting the combined DC output from the strings to alternating current (AC), and a physical interface to AC grid power—typically on the load side of the utility meter, between the meter and the customer's main electrical panel. Alternatively, micro inverters may be used with each panel or N panels (N<=4), obviating the need for a string inverter. The conventional solar energy generation system provides excess AC power back to the AC grid, resulting in cost benefits to the customer.
Conventional solar energy generation systems have been improved to include on-site energy storage. Including energy storage in conventional solar energy generation systems improves the functionality and versatility of such systems. For instance, including on-site energy storage provides a potential source of power when the grid is unavailable, such as when an outage occurs. Additionally, it allows the customer to store the energy generated during the day when the solar array is generating the most power, and then consume that generated power after the sun has set, thereby reducing the customer's peak demand. Distributed storage even has the potential to benefit traditional utilities by allowing their customers to supply power back to the grid at a time when the grid needs additional power, such as to meet mid-day load when active heating or cooling are in use across the grid. Localized energy storage can help utilities stabilize the grid by supplying power to enhance demand response, shaving demand peaks, and shifting loads to times of lower demand. In fact, storage could even take power from the grid instead of the PV system during the middle of the night when supply is high and demand is low. Furthermore, by enabling customers to store energy onsite, it may be possible to bill customers for energy supplied to back-up loads when the grid is unavailable (e.g., during an outage). Managing the operation of such energy generation systems can be very complex. Power can flow between several components in the energy generation system, and successful operation of the energy generation system relies on the absence of conflicting power flow. Given the benefits of solar energy generation systems having on-site energy storage, improvements to the management of power flow in such systems are desired.